The present invention relates to a device for producing drilled holes with an undercut, especially in facing panels.
More particularly, it relates to a device for producing drilled holes with an undercut, which has an adaptor . receiving a drilling tool and joined to a drilling machine so as to transfer torque, and a bearing bush secured in a holding element of a supporting stand and connected with a guide sleeve.
Devices for producing drilled holes with an undercut of the above mentioned general type are known in the art. In the known devices a bearing bush is produced with a rounded depression in which a drilling tool with a collar is supported and mounted to swivel. When the drilling tool swivels out and simultaneously performs a steering movement the lateral cutting edges provided on the drilling tool ream and undercut in the region of the bottom of the drilled hole. An expansible fixing plug with an expansible sleeve can be inserted into the undercut with a matching fit.
The drilled holes with an undercut can be also made in facing panels or similar structures. However, there the undercut must be made very accurately so that when an expansible anchor is inserted and expanded, the expansion pressure produced in this way is not excessively high. Excessively high expansion pressure can result in breaking away a portion of the facing panel. In order to produce an accurate undercut, the drilling tools having a drilling head with diamond chips are utilized. However, it must be noted that the known devices for produced drilled holes with an undercut are inadequate for such impact-sensitive and shock-sensitive drilling tools and for the required accuracy of the drilled holes with an undercut in double-walled facing panels.